By way of corroboration, a paraphrase from Confucius:

  • When I was fifteen I set myself to study.
  • At thirty I knew where to stand.
  • At forty I was no longer confused.
  • At fifty I was able to follow the will of Heaven.
  • At sixty I could hear anything with equanimity.
  • At seventy I was able to do anything I liked without violating moral principles.

A more flippant observation from some quote server: It takes about ten years to get used to how old you are.